First, tumor prevention is divided into three levels: primary prevention, etiological prevention, refers to the adoption of effective measures to avoid or eliminate various carcinogenic factors to reduce the incidence of tumors, which is the most thorough and ideal way to prevent cancer. Secondary prevention, pathogenetic prevention, refers to interfering with the metabolism of carcinogens or inhibiting the combination of carcinogens with the DNA of normal cells in human body, such as certain chemoprevention means which are still under research. Tertiary prevention refers to therapeutic prevention, which is also a way to prevent tumor if the tumor can be cured after suffering from tumor, and it is the primary prevention in the broad sense: 1. pay attention to the balance of diet and nutrition, and do not have partial diet; 2. do not eat the same diet repeatedly, and do not take the same medicine for a long time; 3. eat moderate diet, but not full; 4. do not smoke; 5. consume foods rich in vitamin A, C, E and fiber in appropriate amount; 6. Avoid drinking too much alcohol; 7. Eat less salty and hot food; 8. Eat less burnt food; 9. If you pay attention to these requirements, it is possible to control or eliminate many cancer-causing factors and achieve the purpose of cancer prevention. Breast cancer surveillance Self-examination of breast should be introduced for women over 30 years old, clinical examination should be done once a year for women over 40 years old, and clinical and, if necessary, radiographic screening should be done annually for women over 50 years old. Attention should be paid to high-risk groups such as first pregnancy after 30 years old, first menstruation before 12 years old, menopause after 50 years old, people with obesity, high-fat diet, and history of ovarian disease and endometritis. Cervical cancer surveillance All women who have sex are at risk of developing cervical cancer, and cervical smear examination is usually performed once every 2-3 years since women have sex. Surveillance of colon and rectal cancer People over 40 years old should have an anal finger examination once a year, and people over 50 years old, especially those with family history of tumor, family history of polyps, history of polyp ulcer and history of colorectal cancer, should have a fecal occult blood test once a year, and have a proctoscopy once every 3-5 years. For asymptomatic people, routine lung cancer chest radiological examination and sputum exfoliative cell examination are not necessary. Common symptoms of early stage tumor: 1.lumps in any part of the body such as breast, neck or abdomen, especially those gradually increasing; 2.ulceration in any part of the body such as tongue, cheek and skin without trauma, especially those that do not heal over time; 3.unusual bleeding or discharge, such as irregular vaginal bleeding or increased lab coat in women above middle age; 4.dullness, burning pain and foreign body sensation behind the sternum when eating or progressively aggravated dysphagia; 5. untreated dry cough, hoarseness or blood in sputum; 6. long-term dyspepsia, progressive loss of appetite and weight loss, and no clear cause is identified; 7. change in stool habit or high blood in stool; 8. unilateral headache or with cloth diplopia; 9. sudden enlargement or rupture of black gangrene, bleeding, or loss of original hair; 10. painless hematuria. In conclusion, although malignant tumor is a threat to human life and health